Intermittent fuse blowing Fuse F34 (20A)?

DUTCHINWALES

MEMBER
2015 FORD FIESTA
1.0L
3 CYL
TURBO
2WD
MANUAL
77,000 MILES

Fuse F34 (20A) or the main fuse box blows at random intervals (days/weeks).
As this fuse provides current to the (in-tank) fuel pump and Mass Airflow sensor) the car will quickly stall when this happens (lack of fuel in engine). The only other connection of this fuse is to the ECU. It looks like this connection is only there so the EXU knows if there is a problem (I.E. Blown fuse, or no power to the pump).

Any idea where I should look for the problem? Pump and air sensor have been replaced. Is this likely an intermittent short in the harness? Could there be a short in the ECU? The ECU has 2 connectors; which one is C1831B (I have the wiring diagram and this is where the connection is)?

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,702 POSTS

So, fuse #34 in the main fuse panel goes to the TCM and the high-speed cooling fan up at the radiator. Here are the wiring diagrams so you can see as well. So, 9 times out of 10 it will be the cooling fan motor, I would try to turn it by hand to see if it spins freely. If not replace the cooling fan motor, here is how. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.

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Saturday, October 5th, 2024 AT 2:42 PM

DUTCHINWALES

MEMBER
2 POSTS

Hi Ken,

Thank you so much for taking the time to reply. I know there are many different wiring configurations for the Fiesta, but I’m sure mine has fuse 34 connected to the fuel pump, as per the attached wiring diagram.
Any ideas about the chance of the short being in the ECU?
Thanks!

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